Low-loss compact-size slotted waveguide polarization rotator and transformer.

Two mode-evolution-based low-loss compact-size integrated polarization rotators and transformers are presented. They are designed to fulfill the tasks of rotating mode polarizations between Gaussian-like strip waveguide modes and non-Gaussian-like slotted waveguide modes, as well as the mode transforming between horizontal and vertical slotted waveguides. Consisting of several adiabatic tapers, the presented devices can achieve complete polarization rotations and transformations between different classes of waveguide modes with a device length of tens of micrometers and with a negligible insertion loss.